Measuring flavonoid intake: need for advanced tools

Objective: Flavonoids are phytochemicals with potentially beneficial biological effects that are poorly characterised in existing tables of food composition. Design: To describe new techniques for analysis, absorption, informatics; and dietary assessment that are important in measuring the flavonoid content in foods and in developing a flavonoid food composition database. Setting: Data on chemical analyses of the major flavonoid compounds that exist in the food science literature are being located, collated and compiled into a preliminary flavonoid food composition database. Results: The analytical process begins with preparation of the food for flavonoid analysis using techniques to disrupt the food matrix, alcoholic extraction, and enzymatic or acidic hydrolysis to remove sugars. Separation is usually accomplished using high-performance liquid chromatography. Flavonoids are identified by diode array spectrometry, mass spectrometry or nuclear magnetic resonance spectroscopy. Quantification usually employs comparison of the sample with standards, if available, using the area under the curve of the chromatogram to estimate quantity. Absorption studies are useful since flavonoids vary in their absorption. Finally, information management technologies (informatics) are used to translate flavonoid data information into food composition databases. This process involves identification of foods containing the compounds of interest, collection and organisation of sources of existing analytical data, assignment of quality scores or aggregation of acceptable data for each component and food, calculation of appropriate statistics, assignment of food codes and verification, and finalisation. The resulting food flavonoid database can be used with state-of-the-art dietary assessment methods to develop estimates of flavonoid intakes in foods and to correlate these with estimates of disease risk. Conclusions: A provisional flavonoid database, including at least two components from each of six classes of flavonoids, should be completed in 2002.